There is an increasing need for new and better vaccines, to combat both infectious and malignant disease. This need reflects an increased number of antibiotic- resistant microbes, and new infectious pathogens, as well as potential bioterror organisms. Many current treatments of malignancies rely upon nonspecific and highly toxic medications that cause serious damage to normal organs and tissue as well as malignant cells. Anti-tumor vaccines offer the promise of more specific and effective treatments that better preserve the health and life quality of patients As the Veteran population ages, there is increased incidence of cancer, as well as autoimmune and inflammatory conditions. Our central hypothesis is that understanding how immune responses are regulated by the interplay of multiple signals is key to development of effective immunotherapies, including vaccines. One of the most important sets of such interactions is between signals that activate innate immunity and those that regulate the antigen-specific adaptive immune response. Understanding these interactions is crucial both to understand how the immune response works, and to effectively manipulate immune responses. This basic immunology proposal is focused upon gaining a more complete understanding of how receptors for microbial nucleic acids interact with additional immune receptors in the activation of B lymphocytes, with the long-term goal of applying this knowledge to better strategies in vaccine development. During the current project period, we gained important mechanistic insights into interactions between innate and adaptive immune receptors in B lymphocytes. These insights were applied both to the regulation of responsiveness to signals via the toll-like receptors (TLR) of the innate immune system, and use of B cells as cellular vaccines. The work proposed for the next project period builds upon these findings to gain additional mechanistic insights and optimize B cell vaccine effectiveness. We will pursue two major experimental Aims: 1) To optimize the interaction of innate and adaptive immune receptor interactions in B cell vaccines, using both a model response to an infectious pathogen and a tumor model, and 2) To examine the interplay between signals delivered via the B cell antigen receptor, toll-like receptors, and interferon receptors in B cell activation, innate immune tolerance, and B cell vaccination.